git doc: direct bug reporters to mailing list archive

The mailing list archive can help a user encountering a bug to tell
whether a recent regression has already been reported and whether a
longstanding bug has already had some discussion to start their
thinking.

Based-on-patch-by: Martin Ågren <martin.agren@gmail.com>
Improved-by: Junio C Hamano <gitster@pobox.com>
Improved-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git.txt

@@ -858,7 +858,9 @@ Reporting Bugs
 
 Report bugs to the Git mailing list <git@vger.kernel.org> where the
 development and maintenance is primarily done.  You do not have to be
-subscribed to the list to send a message there.
+subscribed to the list to send a message there.  See the list archive
+at https://public-inbox.org/git for previous bug reports and other
+discussions.
 
 Issues which are security relevant should be disclosed privately to
 the Git Security mailing list <git-security@googlegroups.com>.